[Rubix]

I have a question regarding liquid/liquid extraction following derivatization of aldehydes with pentafluorobenzyl hydroxylamine (PHBHA). I have attached the reaction scheme below.

According to a procedure I'm following, the pentafluorobenzyl-oxime is extracted into hexane while the excess PFBHA remains in the aqueous phase.

I am a little confused as to why the pentafluorobenzyl-oxime moves into the organic solvent phase. I would assume that the F, O and N atoms still present on the pentafluorobenzyl-oxime would be able to form hydrogen bonds with water and still remain in the aqueous phase? Thanks for helping me out!

[LigteV]

The answer has to do with the pKa value of the amine or amide and the pH of your water solution..